Optical wavelength identifying system

ABSTRACT

An optical wavelength identifying system comprises an optical wavelength detecting device, a memory, a modulator, a comparison module, and an instruction module. The optical wavelength detecting device comprises a polarizer, a detecting element, a measuring device and a data processor. The polarizer is configured to transform an incident light into a polarized light. The detecting element is configured to form a temperature difference or a potential difference, wherein the detecting element comprises a carbon nanotube structure comprising a plurality of carbon nanotubes oriented along the same direction. The measuring device is electrically connected to the detecting element and configured to measure the temperature difference or the potential difference. The data processor is electrically connected to the measuring device and configured to obtain the optical wavelength by calculating and analyzing the temperature difference or the potential difference.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. §119 fromChina Patent Application No. 201610042562.1, filed on Jan. 22, 2016, inthe China Intellectual Property Office, the disclosure of which isincorporated herein by reference.

FIELD

The subject matter herein generally relates to an optical wavelengthidentifying system.

BACKGROUND

It has always been an interesting topic for people to explore usages ofspecific wavelengths of light. For example, the light can show differentcolors because of different wavelengths of light, and the light can bedirectly used as indicator tools in our life. Certainly, the lighthaving specific wavelength can be applied to many fields. But in thestudy of the specific wavelength of light application, it is necessaryto be able to measure the wavelength simply and accurately.

Currently, there are some methods of measuring the specific wavelength,such as measurement using light interference, or measurement using lightdiffraction. But these methods are carried out manually and complicated,and workers who carry out these methods must have high levels. Also,measurement errors of these methods are large, and the measurement scaleis limited. The detection equipment related to these methods are verybig and complicated.

What is needed, therefore, is to provide a system for identifyingoptical wavelength for solving the problem discussed above.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referencesto the following drawings. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views. Implementations of the present technologywill now be described, by way of example only, with reference to theattached figures, wherein:

FIG. 1 is a schematic view of an optical wavelength identifying system.

FIG. 2 is a schematic view of one embodiment of an optical wavelengthdetecting device.

FIG. 3 is a structural schematic view of one embodiment of a drawncarbon nanotube film.

FIG. 4 shows a Scanning Electron Microscope (SEM) image of oneembodiment of the drawn carbon nanotube film.

FIG. 5 is a SEM image of one embodiment of a non-twisted carbon nanotubewire.

FIG. 6 is a SEM image of one embodiment of a twisted carbon nanotubewire.

FIG. 7 is a diagram showing a relationship between a light transmittanceof a carbon nanotube structure and an optical wavelength.

FIG. 8 is a schematic view of stacked arrangements of semiconductorcarbon nanotube layers.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. The drawings are not necessarily to scale, andthe proportions of certain parts may be exaggerated to better illustratedetails and features. The description is not to be considered aslimiting the scope of the embodiments described herein.

Several definitions that apply throughout this disclosure will now bepresented.

The connection can be such that the objects are permanently connected orreleasably connected. The term “substantially” is defined to beessentially conforming to the particular dimension, shape or other wordthat substantially modifies, such that the component need not be exact.The term “comprising” means “including, but not necessarily limited to”;it specifically indicates open-ended inclusion or membership in aso-described combination, group, series and the like. It should be notedthat references to “an” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

Referring to FIG. 1, an optical wavelength identifying system 10comprises a receiver 110, an optical wavelength detecting device 100, amodulator 130, a memory 140, a comparison module 160 and an instructionmodule 170. The receiver 110 is used for collecting incident light andtransmitting the incident light to the optical wavelength detectingdevice 100. The optical wavelength detecting device 100 is used forconverting and calculating the incident light to obtain opticalwavelength. The memory 140 is used to store standard data in a standarddatabase of transmittance-angle-wavelength values and a predeterminedvalue. The modulator 130 is used to set or reset the predeterminedvalue. The comparison module 160 is configured to compare the opticalwavelength with the predetermined value to obtain a comparison result.The instruction module 170 is used to send work instructions accordingto the comparison result.

The receiver 110 is used for collecting the incident light. For example,a divergent light can be collected into a beam of light by the receiver110. It can be understood that the receiver 110 is not necessary whenthe incident light gathers well. The receiver 110 is a device that cancollect light, such as a concave mirror. In one embodiment, the receiver110 is a concave mirror.

The optical wavelength detecting device 100 is used for converting andcalculating the incident light to obtain optical wavelength. The opticalwavelength detecting device 100 can convert the incident light into apotential difference or a temperature difference. The optical wavelengthof the incident light can be obtained by analyzing and calculating thepotential difference or temperature difference.

Referring to FIG. 2, the optical wavelength detecting device 100comprises a polarizer 101, a detecting element 102, a first electrode103, a second electrode 104, a measuring device 105 and a data processor108. The polarizer 101 is spaced from the detecting element 102 and usedfor generating polarized light. The first electrode 103 and the secondelectrode 104 are spaced apart from each other and electricallyconnected to the detecting element 102. The detecting element 102 iselectrically connected to the measuring device 105 by the firstelectrode 103 and the second electrode 104. The detecting element 102comprises a carbon nanotube structure. The carbon nanotube structurecomprises a plurality of carbon nanotubes oriented along the samedirection and is in direct contact with the first electrode 103 and thesecond electrode 104. The measuring device 105 is electrically connectedto the first electrode 103 and the second electrode 104. The dataprocessor 108 is connected to the measuring device 105.

The polarizer 101 and the detecting element 102 are parallel and spacedfrom each other. The polarized light emitting from the polarizer 101 canirradiate the carbon nanotube structure of the detecting element 102. Anoriented direction of the carbon nanotubes of the carbon nanotubestructure can be the same as a direction from the first electrode 103 tothe second electrode 104. The measuring device 105 is used to measure atemperature difference or potential difference of the carbon nanotubestructure. A light transmittance can be obtained by calculating thedifference of temperature or potential, and the optical wavelength canbe obtained by reading the light transmittance.

The polarizer 101 is used for transforming light into polarized light.The polarizer 101 can be any kinds of materials that can transform lightinto polarized light. The polarizer 101 can be yttrium aluminate,iodine, calcite or any other suitable material. The polarizer 101 can bea rotatable structure to form any angles between a polarized lightdirection and the oriented direction of the carbon nanotubes. Thepolarizer 101 can be rotated in a plane of the polarizer 101 to alterthe angles between the direction of the polarized light and the orienteddirection of the carbon nanotubes. Thus the angles between the polarizedlight direction and the oriented direction of the carbon nanotubes canbe at any value in 0-90 degree.

The detecting element 102 comprises the carbon nanotube structure. Thecarbon nanotube structure comprises a plurality of carbon nanotubesoriented along the same direction. The oriented direction of carbonnanotubes is parallel with a carbon nanotube structure surface. In oneembodiment, the detecting element 102 is a carbon nanotube layer, andthe carbon nanotube layer consists of a plurality of carbon nanotubes,joined to each other end to end by van der Waals attractive force. Thecarbon nanotubes in the carbon nanotube structure can be single-walled,double-walled, or multi-walled carbon nanotubes. A diameter of eachsingle-walled carbon nanotube ranges from about 0.5 nanometers (nm) toabout 10 nm. A diameter of each double-walled carbon nanotube rangesfrom about 1 nm to about 15 nm. A diameter of each multi-walled carbonnanotube ranges from about 1.5 nm to about 50 nm. The carbon nanotubescan be N-type carbon nanotubes or P-type carbon nanotubes.

The carbon nanotube structure can be a free-standing structure. Thefree-standing structure is that the carbon nanotube structure can keep acertain shape without any supporter, which is different from powder orliquid. The carbon nanotube structure comprises a plurality of carbonnanotubes joined to each other by van der Waals attractive force,thereby forming a certain shape. When the carbon nanotube structure is afree-standing structure, the detecting element 102 can be suspended. Thecarbon nanotube structure comprises at least one carbon nanotube film,at least one carbon nanotube wire structure, or a combination thereof.The carbon nanotube structure is a layer structure of a plurality ofparallel arrangement carbon nanotubes.

Carbon Nanotube Film

In one embodiment, the carbon nanotube film comprises at least onecarbon nanotube segment. Referring to FIG. 3, each carbon nanotubesegment 143 comprises a plurality of carbon nanotubes 145 approximatelyparallel to each other, and combined by van der Waals attractive force.The carbon nanotube segments 143 can vary in width, thickness,uniformity, and shape. The carbon nanotubes 145 in the carbon nanotubesegments 143 are also oriented along a preferred orientation.

Carbon Nanotube Film Manufactured by Method 1

In one embodiment, the carbon nanotube film can be drawn from a carbonnanotube array, to form a drawn carbon nanotube film. In the presentembodiment, the drawn carbon nanotube film can be pulled out from asuper-aligned carbon nanotube array on a substrate. The drawn carbonnanotube film comprises a plurality of successive and oriented carbonnanotubes 145 joined end to end by van der Waals attractive force.Referring to FIG. 4, each drawn carbon nanotube film comprises aplurality of successively oriented carbon nanotube segments 143 joinedend-to-end by van der Waals attractive force. The thickness of the drawncarbon nanotube film is in a range from about 0.5 nm to about 100micrometers (μm). Examples of a drawn carbon nanotube film are taught byU.S. Pat. No. 7,045,108 to Jiang et al., and WO 2007015710 to Zhang etal.

Carbon Nanotube Film Manufactured by Method 2

In another embodiment, the carbon nanotube film comprises one carbonnanotube segment 143. Referring to FIG. 4, the carbon nanotube segment143 comprises a plurality of carbon nanotubes 145 substantially arrangedalong the same direction. The carbon nanotubes 145 in the carbonnanotube film are substantially parallel to each other and have almostequal lengths, and are combined side by side via van der Waalsattractive force. The width of the carbon nanotube film is equal to thelength of the carbon nanotubes 145, thus at least one carbon nanotube145 spans the entire width of the carbon nanotube film. The carbonnanotube film can be produced by growing a strip-shaped carbon nanotubearray, and pushing the strip-shaped carbon nanotube array down along adirection substantially perpendicular to a length of the strip-shapedcarbon nanotube array, and has a length of about 20 μm to about 10millimeters (mm). The length of the carbon nanotube film is only limitedby the length of the strip. A larger carbon nanotube film also can beformed by having a plurality of the strips lined up side by side andfolding the carbon nanotubes 145 grown thereon over such that there isoverlap between the carbon nanotubes 145 on adjacent strips.

Carbon Nanotube Film Manufactured by Method 3

In some embodiments, the carbon nanotube film comprising one carbonnanotube segment 143 can also be produced by a method adopting a“kite-mechanism.” The carbon nanotube film can have carbon nanotubes 145with a length greater than 10 centimeters (cm). The carbon nanotube filmcan be produced by providing a growing substrate with a catalyst layerlocated thereon, placing the growing substrate adjacent to theinsulating substrate in a chamber, heating the chamber to a growthtemperature for carbon nanotubes 145 under a protective gas, introducinga carbon source gas along a gas flow direction, and growing a pluralityof carbon nanotubes 145 on the insulating substrate. After introducingthe carbon source gas into the chamber, the carbon nanotubes 145 willstart to grow under the effect of the catalyst. One end (e.g., the root)of the carbon nanotubes 145 is kept unchanged on the growing substrate,and the other end (e.g., the top/free end) of the carbon nanotubes 145will grow continuously. The growing substrate is near an inlet of theintroduced carbon source gas, such that the carbon nanotubes 145 floatsabove the insulating substrate with the roots of the carbon nanotubes145 still attached on the growing substrate, as the carbon source gas iscontinuously introduced into the chamber. The length of the carbonnanotubes 145 depends on the growth conditions. After growth has beenstopped, the carbon nanotubes 145 are located entirely on the insulatingsubstrate. The carbon nanotubes 145 roots are then separated from thegrowing substrate. This can be repeated many times to obtain many layersof carbon nanotube films on a single insulating substrate. The adjacentcarbon nanotubes 145 can be adhered together by van der Waals attractiveforce and being substantially parallel to each other, with a distance ofadjacent carbon nanotubes 145 being less than 5 μm.

The carbon nanotube structure can comprise at least two stacked and/orcoplanar carbon nanotube films. These coplanar carbon nanotube films canalso be stacked one upon other films. The carbon nanotubes 145 in twoadjacent carbon nanotube films are substantially parallel. Adjacentcarbon nanotube films can be combined only by the van der Waalsattractive force. The number of layers of the carbon nanotube films isnot limited so that a carbon nanotube structure can have differentwidths and areas. Stacking the carbon nanotube films will add to thestructural strength of the carbon nanotube structure.

Carbon Nanotube Wire Structure

In other embodiments, the carbon nanotube structure comprises one ormore carbon nanotube wire structures. The carbon nanotube wire structurecomprises carbon nanotube cables that comprise of twisted carbonnanotube wires, untwisted carbon nanotube wires, or combinationsthereof. The carbon nanotube cable comprises two or more carbon nanotubewires, twisted or untwisted that are twisted or bundled together. Thecarbon nanotube wires in the carbon nanotube wire structure can besubstantially parallel to each other to form a bundle-like structure ortwisted with each other to form a twisted structure. When the carbonnanotube structure comprises a plurality of carbon nanotube wirestructures, the carbon nanotube wire structures can be coplanar andsubstantially parallel to each other, or stacked and substantiallyparallel to each other. When the carbon nanotube structure comprises onecarbon nanotube wire structure, the carbon nanotube wire structure bendsorderly in a surface, thereby forming a planar structure, and the carbonnanotube wires of the carbon nanotube wire structure are substantiallyparallel to and connect to each other and arranged.

The non-twisted carbon nanotube wire can be formed by treating the drawncarbon nanotube film with an organic solvent. The drawn carbon nanotubefilm is treated by applying the organic solvent to the drawn carbonnanotube film to soak the entire surface of the drawn carbon nanotubefilm. After being soaked by the organic solvent, the adjacent parallelcarbon nanotubes in the drawn carbon nanotube film will bundle together,due to the surface tension of the volatile organic solvent as theorganic solvent volatilizes, and thus, the drawn carbon nanotube filmwill be shrunk into a non-twisted carbon nanotube wire. Referring toFIG. 5, the non-twisted carbon nanotube wire comprises a plurality ofcarbon nanotubes substantially oriented along the same direction (e.g.,a direction along the length of the non-twisted carbon nanotube wire).The carbon nanotubes are substantially parallel to the axis of thenon-twisted carbon nanotube wire. The non-twisted carbon nanotube wirecomprises a plurality of carbon nanotube segments joined end-to-end byvan der Waals attractive force. Each carbon nanotube segment comprises aplurality of carbon nanotubes substantially parallel to each other andcombined by van der Waals attractive force. A length of the non-twistedcarbon nanotube wire can be arbitrarily set as desired. A diameter ofthe non-twisted carbon nanotube wire can range from about 0.5 nm toabout 100 μm. In one embodiment, the diameter of the non-twisted carbonnanotube wire is about 50 μm. Examples of the non-twisted carbonnanotube wire are taught by US Patent Application Publication US2007/0166223 to Jiang et al.

The twisted carbon nanotube wire can be formed by twisting a drawncarbon nanotube film by using a mechanical force to turn the two ends ofthe drawn carbon nanotube film in opposite directions. Referring to FIG.6, the twisted carbon nanotube wire comprises a plurality of carbonnanotubes oriented along an axial direction of the twisted carbonnanotube wire. The carbon nanotubes are aligned in a helix around theaxis of the carbon nanotube twisted wire. More specifically, the twistedcarbon nanotube wire comprises a plurality of successive carbon nanotubesegments joined end-to-end by van der Waals attractive force. Eachcarbon nanotube segment comprises a plurality of carbon nanotubessubstantially parallel to each other and combined by van der Waalsattractive force. The carbon nanotube segment has arbitrary length,thickness, uniformity, and shape. A length of the carbon nanotube wirecan be arbitrarily set as desired. A diameter of the twisted carbonnanotube wire can range from about 0.5 nm to about 100 μm. Further, thetwisted carbon nanotube wire can be treated with a volatile organicsolvent, before or after being twisted. After being soaked by theorganic solvent, the adjacent parallel carbon nanotubes in the twistedcarbon nanotube wire will bundle together, due to the surface tension ofthe organic solvent as the organic solvent volatilizes. The specificsurface area of the twisted carbon nanotube wire will decrease, but thedensity and strength of the twisted carbon nanotube wire will increase.It is understood that the twisted and non-twisted carbon nanotube cablescan be produced by methods that are similar to the methods of makingtwisted and non-twisted carbon nanotube wires.

In one embodiment, the carbon nanotube structure is composed of at leastone carbon nanotube film and at least one carbon nanotube wirestructure. The carbon nanotubes in the carbon nanotube film aresubstantially parallel to the carbon nanotube wire structures.

The thickness of the carbon nanotube structure can be selected asdesired. The carbon nanotube structure is thick enough to guarantee thatthe detecting element 102 can detect the wavelength and the measurederror is small. In one embodiment, the thickness of the carbon nanotubestructure can range from about 0.5 nm to about 5 μm. The thickness ofthe carbon nanotube structure cannot be too thick (greater than 5 μm).If the thickness of the carbon nanotube structure is greater than 5 μm,because the incident light cannot pass through the carbon nanotubestructure, a part of the carbon nanotubes cannot be irradiated by thelight. The optical wavelength detecting device 100 has a largemeasurement error.

Referring to FIG. 7, in the carbon nanotube structure, the carbonnanotubes are substantially parallel and extend along the samedirection, the polarized light is selectively absorbed by the carbonnanotube structure according to the polarized light direction andpolarized light wavelength. As an angle between the polarized lightdirection and the carbon nanotubes is unchanged, the polarized lighttransmittance increases monotonously as the wavelength increases. Whenthe polarized light wavelength is kept unchanged, the angle changes canmake the polarized light transmittance being changed. When thepolarizing direction is substantially parallel to the carbon nanotubesorientation, the polarized light is easily absorbed by the carbonnanotube structure, so the polarized light transmittance is very low.When the polarizing direction is substantially perpendicular to thecarbon nanotubes orientation, the polarized light can pass through thecarbon nanotube structure easily, so the polarized light transmittanceis very high. Due to the polarized light absorbed by the carbon nanotubestructure can be converted into heat energy, the heat energy can producetemperature difference in the carbon nanotube structure and thetemperature difference can change into the potential difference. Thecarbon nanotube structure can measure the polarized light wavelength asthe temperature and voltage changes.

The carbon nanotube structure further comprises a P-N junction composedof a P-type semiconductor carbon nanotube layer 2021 and an N-typesemiconductor carbon nanotube layer 2022. The P-type semiconductorcarbon nanotube layer 2021 and the N-type semiconductor carbon nanotubelayer 2022 can be stacked with each other or arranged side by side inthe same plane. When the P-type semiconductor carbon nanotube layer 2021and the N-type semiconductor carbon nanotube layer 2022 are arrangedside by side in the same plane, the oriented direction of carbonnanotubes in the P-type semiconductor carbon nanotube layer 2021 is thesame as the oriented direction of carbon nanotubes in the N-typesemiconductor carbon nanotube layer 2022. And a contact surface of theP-type semiconductor carbon nanotube layer 2021 and the N-typesemiconductor carbon nanotube layer 2022 is perpendicular to theoriented direction of carbon nanotubes. When the P-type semiconductorcarbon nanotube layer 2021 and the N-type semiconductor carbon nanotubelayer 2022 are stacked with each other, the contact surface of theP-type semiconductor carbon nanotube layer 2021 and the N-typesemiconductor carbon nanotube layer 2022 is parallel to the orienteddirection of carbon nanotubes. Referring to FIG. 8, the stackedarrangement can also be sandwich structure, such as P-N-P or N-P-N. Itis necessary to satisfy that the P-type semiconductor carbon nanotubelayer 2021 and the N-type semiconductor carbon nanotube layer 2022 areelectrically connected to the first electrode 203 and the secondelectrode 204. When the N-type semiconductor carbon nanotube layer issandwiched between a first P-type semiconductor carbon nanotube layerand a second P-type semiconductor carbon nanotube layer, a first part ofthe N-type semiconductor carbon nanotube layer extends to the outside ofthe two P-type semiconductor carbon nanotube layers to form an exposedpart, and the exposed part of the N-type semiconductor carbon nanotubelayer is coated by the second electrode 204. Additionally, the firstelectrode 203 comprises a first electrode unit and a second electrodeunit, the first electrode unit is located on a second part of the firstP-type semiconductor carbon nanotube layer, the second electrode unit islocated on a third part of the second P-type semiconductor carbonnanotube layer. And the first electrode unit and the second electrodeunit are electrically connected with each other. When the P-typesemiconductor carbon nanotube layer is sandwiched between a first N-typesemiconductor carbon nanotube layer and a second N-type semiconductorcarbon nanotube layer, a first part of the P-type semiconductor carbonnanotube layer extends to the outside of the two N-type semiconductorcarbon nanotube layers to form an exposed part, and the exposed part ofthe P-type semiconductor carbon nanotube layer is coated by the secondelectrode 204. And the first electrode 203 comprises a first electrodeunit and a second electrode unit, the first electrode unit is located ona second part of the first N-type semiconductor carbon nanotube layer,the second electrode unit is located on a third part of the secondN-type semiconductor carbon nanotube layer. And the first electrode unitand the second electrode unit are electrically connected with eachother. In one embodiment, the P-type semiconductor carbon nanotube layer2021 and the N-type semiconductor carbon nanotube layer 2022 arearranged side by side in the same plane.

When the carbon nanotube structure containing P-N junction is irradiatedby the incident light, the incident light energy is directly convertedinto electrical energy and is not converted into heat energy. Thetemperature difference between a portion of the carbon nanotubestructure irradiated with the incident light and a non-irradiatedportion is small and negligible. In one embodiment, the effect ofincident light on carbon nanotubes is changed from thermoelectric effectto photoelectric effect, which reduced the loss of intermediate energy.The structure with P-N junction enhances the sensitivity of the carbonnanotube structure to the incident light, thus the measurement of thedevice is more accurate.

In one embodiment, the detecting element 102 can further comprise aninsulating substrate 106 for supporting the carbon nanotube structure.The carbon nanotube structure is located on an insulating substrate 106surface. The insulating substrate 106 material can be rigid materials(e.g., p-type or n-type silicon, silicon with a silicon dioxide layerformed thereon, crystal, crystal with an oxide layer formed thereon), orflexible materials (e.g., plastic or resin). The insulating substrate106 material can be polyethylene terephthalate, polyethylene naphthalatetwo formic acid glycol ester (PEN), or polyimide. In one embodiment, thedetecting element 102 comprises an insulating substrate 106, and theinsulating substrate 106 material is poly ethylene terephthalate.

In one embodiment, the detecting element 102 can be rotated freely inthe detecting element plane to form different angles between thepolarized light direction and the carbon nanotubes orientation. Thepolarizer 101 can also be rotated freely in the polarizer 101 plane toadjust the angles between the polarized light direction and the carbonnanotubes orientation.

The first electrode 103 and the second electrode 104 are made ofconductive material. The first electrode 103 or the second electrode 104shape is not limited and can be lamellar, rod, wire, block, or othershapes. A first and second electrodes 103, 104 material can be one metalor more metals, conductive adhesive, carbon nanotube, indium tin oxide,or other material. In one embodiment, the first electrode 103 and thesecond electrode 104 are rod-shaped metal electrodes. The carbonnanotubes in the carbon nanotube structure extend along a direction fromthe first electrode 103 to the second electrode 104. Some carbonnanotube structures have large specific surface area and better adhesionability under the effect of the van der Waals attractive force and canbe adhered directly to the first electrode 103 and the second electrode104. This will result in good electrical contact between the carbonnanotube structure and the first and second electrodes 103, 104.Furthermore, a conductive adhesive layer (not shown) can be furtherprovided between the first electrode 103 and/or the second electrode 104and the carbon nanotube structure. The conductive adhesive layer can beapplied to the carbon nanotube structure surface to provide electricalcontact and better adhesion between the first and second electrodes 103,104 and the carbon nanotube structure.

The measuring device 105 can be a voltage measuring device to measurethe carbon nanotube structure voltage differences or a thermocoupledevice to measure the temperature differences of the carbon nanotubestructure. The measuring device 105 can be electrically connected to thecarbon nanotube structure by the first electrode 103 and the secondelectrode 104, thus a circuit is formed. When the carbon nanotubestructure generates a potential between the first electrode 103 and thesecond electrode 104 because of the temperature difference, the carbonnanotube structure is equivalent to a power, and a current is generatedin the circuit. The measuring device 105 can measure the carbon nanotubestructure potential directly without any other power supply device. Whenthe measuring device 105 is the thermocouple device, the thermocoupledevice can measure the temperature difference between the opposite twoends of the carbon nanotube structure. A measuring position can beselected as desired. When the polarized light irradiates a first partsurface of the carbon nanotube structure, a first point in the firstpart surface which is irradiated is selected, a second point in a secondpart surface which is not irradiated is selected, the measuring device105 measures the temperature difference or the potential differencebetween the first point and the second point. The carbon nanotubestructure can further comprise a P-type semiconductor carbon nanotubelayer and an N-type semiconductor carbon nanotube layer in contact witheach other to form a P-N junction. A third point in the P-typesemiconductor carbon nanotube layer is selected, a fourth point in theN-type semiconductor carbon nanotube layer is selected. The measuringdevice 105 can only measure the potential difference between the thirdpoint and the fourth point when the polarized light irradiates the P-Njunction.

The data processor 108 is used to obtain the optical wavelength bycalculating and analyzing the temperature difference or the potentialdifference. The data processor 108 comprise a database oftransmittance-angle-wavelength values and can calculate the temperaturedifference or the potential difference to obtain the polarized lighttransmittance. Then the optical wavelength can be obtained according tothe values of transmittance in the database oftransmittance-angle-wavelength values.

The principle of measuring the optical wavelength by using the opticalwavelength detecting device 100 can be further described in detail.Firstly, a beam of incident light is provided, and the incident lightpower is determined. The power is set to P, and the optical wavelengthis set to λ. Secondly, the polarized light is formed by using thepolarizer 101 to polarize the incident light. There is an amount ofenergy loss during the incident light passing through the polarizer 101.A transmittance of the polarizer is set to α. Referring to FIG. 7, asthe angle between the polarized light direction and the carbon nanotubeschanges, the polarized light transmittances are different. Thetransmittance is set to T. When the polarizing direction issubstantially parallel to the carbon nanotubes orientation, thetransmittance is set to T_(λII). When the polarizing direction issubstantially perpendicular to the carbon nanotubes orientation, thetransmittance is set to T_(λ⊃). When the polarized light irradiates thecarbon nanotube structure, an electric potential is produced by thetemperature difference induced in the carbon nanotube structure. Anenergy conversion efficiency is set to β. The energy conversionefficiency β is only related to devices comprising carbon nanotubes andis not related to the carbon nanotubes orientation.

So a potential difference U of both carbon nanotube structure ends isdefined by a formula (1),u=√{square root over (PRαβ(1-T))}  (1)R is a carbon nanotube structure resistance. The carbon nanotubestructure resistance is approximately unchanged despite the temperaturevariation range is not large. At the same time, a carbon nanotubestructure has been determined, the resistance is kept unchanged andisn't related to the polarization direction of light and wavelength.

The polarizing direction is substantially parallel to the carbonnanotubes orientation, the potential difference of the carbon nanotubestructure is U_(II),U _(II)=√{square root over (PRαβ(1-T _(λII)))}.

The polarizing direction is substantially perpendicular to the carbonnanotubes orientation, the potential difference of the carbon nanotubestructure is U_(⊥),U _(⊥)=√{square root over (PRαβ(1-T _(λ⊥)))}K is defined,

$\mspace{79mu}{{K = \frac{U_{\coprod}}{U_{\bot}}},{K = {\frac{U_{\coprod}}{U_{\bot}} = {\sqrt{\frac{1 - T_{\lambda\coprod}}{1 - T_{\lambda\bot}}} = {\sqrt{\frac{1 - T_{\lambda\bot} + T_{\lambda\bot} - T_{\lambda\coprod}}{1 - T_{\lambda\bot}}} = \sqrt{1 + \frac{T_{\lambda\bot} - T_{\lambda\coprod}}{1 - T_{\lambda\bot}}}}}}}}$

When the angle between the carbon nanotubes orientation and polarizingdirection is unchanged, a transmittance difference between arbitrarywavelength is approximately kept unchanged.T _(λ⊥)-T _(λII) =C, the C is unchanged.

$\begin{matrix}{K = {\sqrt{1 + \frac{T_{\lambda\bot} - T_{\lambda\coprod}}{1 - T_{\lambda\bot}}} = \sqrt{1 + \frac{C}{1 - T_{\lambda\bot}}}}} & (2)\end{matrix}$

Referring to the formula (2), the values of K and T_(λ⊥) are monotonic.When the angle between the carbon nanotubes orientation and polarizingdirection is unchanged, the value of T_(λ⊥) increases as the wavelengthincreases. So the values of K and wavelength of incident light aremonotonic.

A formula (3) can be obtained by changing the formula (2),

$\begin{matrix}{T_{\lambda\bot} = {1 - \frac{C}{K^{2} - 1}}} & (3)\end{matrix}$

Referring to the formula (3), T_(λ⊥) can be obtained by calculating thevalue of K. The value of K can be obtained by calculating the values ofU_(II) and U_(⊃) of the carbon nanotube structure under differentconditions. When the angle between the carbon nanotubes orientation andpolarizing direction is unchanged, the polarized light transmittancecorresponds to a unique wavelength value. The optical wavelength can beobtained according to the values of transmittance in the database oftransmittance-angle-wavelength values of the data processor 108.According to the Seebeck effect, U=ρ ΔT, ρ is the Seebeck coefficientand related to materials. The temperature differences change as thevoltage value changes, and the wavelength value of incident light canalso be calculated by the temperature differences.

The memory 140 is used to store the standard database oftransmittance-angle-wavelength values and the predetermined values. Andthe wavelength in the standard database is equal to or greater than 300nm. The wavelength values in the standard database are standard data,and the standard data can be provided for the subsequent measurement.

The modulator 130 is connected to the memory 140, and the modulator 130is configured to set or reset the predetermined values. Thepredetermined values are chose from the standard database. The modulator130 can also update the standard database in the memory 140.

The comparison module 160 is configured to compare the opticalwavelength with the predetermined value to obtain a comparison result.The instruction module 170 is used to send work instructions accordingto the comparison result. Also a plurality of different predeterminedvalues can be set to correspond to different work instructions. When theoptical wavelength detected by the optical wavelength detecting device100 is the same as one of the predetermined values, the instructionmodule 170 would send a work instruction.

In use, the optical wavelength identifying system 10 can be connected toa working device 150. The working device 150 is directly connected tothe instruction module 170. When the specific optical wavelengthidentifying system 10 receive incident light, the instruction module 170can send a work instruction to the working device 150 according to thecomparison result. The working device 150 receives the work instructionand perform an operation according to the work instruction.

The optical wavelength identifying system 10 has following advantages.Due to the carbon nanotube structure composed of a plurality of carbonnanotubes, the optical wavelength can be measured by processing thelight passing through the carbon nanotube structure. The method ofmeasuring the optical wavelength is simple. The carbon nanotubestructure can also play the role of power, so a special power supply isnot required in the optical wavelength identifying system 10. Theoptical wavelength identifying system 10 structure is simple.

The embodiments shown and described above are only examples. Even thoughnumerous characteristics and advantages of the present technology havebeen set forth in the foregoing description, together with details ofthe structure and function of the present disclosure, the disclosure isillustrative only, and changes may be made in the detail, including inmatters of shape, size and arrangement of the parts within theprinciples of the present disclosure up to, and including, the fullextent established by the broad general meaning of the terms used in theclaims.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. The description and the claims drawn to a method may includesome indication in reference to certain steps. However, the indicationused is only to be viewed for identification purposes and not as asuggestion as to an order for the steps.

What is claimed is:
 1. An optical wavelength identifying system, thesystem comprising: an optical wavelength detecting device configured todetect an optical wavelength of an incident light, comprising: apolarizer configured to transform the incident light into a polarizedlight; a detecting element configured to form a temperature differenceor a potential difference between two points of the detecting elementwhen exposed to the polarized light, wherein the detecting elementcomprises a carbon nanotube structure that comprises a plurality ofcarbon nanotubes oriented along a first direction, and angles between apolarizing direction of the polarized light and the first direction ofthe plurality of carbon nanotubes is adjustable; a measuring deviceelectrically connected to the detecting element and configured tomeasure the temperature difference or the potential difference; a dataprocessor electrically connected to the measuring device and configuredto obtain the optical wavelength by calculating and analyzing thetemperature difference or the potential difference; a memory configuredto store a predetermined value and a standard database oftransmittance-angle-wavelength values and predetermined values; amodulator configured to set or reset the predetermined value; acomparison module configured to compare the optical wavelength of theincident light with the predetermined value to obtain a comparisonresult; and an instruction module configured to send a work instructionaccording to the comparison result.
 2. The system as claimed in claim 1,wherein the polarizer is rotatable to adjust the angles between thepolarizing direction of the polarized light and the first direction ofthe plurality of carbon nanotubes.
 3. The system as claimed in claim 1,further comprising a receiver for collecting the incident light.
 4. Thesystem as claimed in claim 1, wherein the detecting element issuspended.
 5. The system as claimed in claim 1, wherein the detectingelement is a carbon nanotube layer, and the carbon nanotube layercomprises a plurality of carbon nanotubes, connected to each other endto end by van der Waals attractive force.
 6. The system as claimed inclaim 1, wherein the optical wavelength detecting device furthercomprises a first electrode and a second electrode, and the firstelectrode and the second electrode are electrically connected to thecarbon nanotube structure.
 7. The system as claimed in claim 1, whereinthe detecting element comprises a P-type semiconductor carbon nanotubelayer and an N-type semiconductor carbon nanotube layer, a P-N junctionis formed between the P-type semiconductor carbon nanotube layer and theN-type semiconductor carbon nanotube layer, and the measuring device isrespectively electrically connected to the P-type semiconductor carbonnanotube layer and the N-type semiconductor carbon nanotube layer. 8.The system as claimed in claim 7, wherein the P-type semiconductorcarbon nanotube layer and the N-type semiconductor carbon nanotube layerare stacked with each other.
 9. The system as claimed in claim 8,wherein the N-type semiconductor carbon nanotube layer is sandwichedbetween a first P-type semiconductor carbon nanotube layer and a secondP-type semiconductor carbon nanotube layer, a first part of the N-typesemiconductor carbon nanotube layer extends to the outside of the twoP-type semiconductor carbon nanotube layers to form an exposed part, andthe exposed part of the N-type semiconductor carbon nanotube layer iscoated by the second electrode; the first electrode comprises a firstelectrode unit and a second electrode unit, the first electrode unit islocated on a second part of the first P-type semiconductor carbonnanotube layer, the second electrode unit is located on a third part ofthe second P-type semiconductor carbon nanotube layer, and the firstelectrode unit and the second electrode unit are electrically connectedwith each other.
 10. The system as claimed in claim 8, wherein theP-type semiconductor carbon nanotube layer is sandwiched between a firstN-type semiconductor carbon nanotube layer and a second N-typesemiconductor carbon nanotube layer, a first part of the P-typesemiconductor carbon nanotube layer extends to the outside of the twoN-type semiconductor carbon nanotube layers to form an exposed part, andthe exposed part of the P-type semiconductor carbon nanotube layer iscoated by the second electrode; and the first electrode comprises afirst electrode unit and a second electrode unit, the first electrodeunit is located on a second part of the first N-type semiconductorcarbon nanotube layer, the second electrode unit is located on a thirdpart of the second N-type semiconductor carbon nanotube layer, and thefirst electrode unit and the second electrode unit are electricallyconnected with each other.
 11. The system as claimed in claim 6, whereinthe P-type semiconductor carbon nanotube layer and the N-typesemiconductor carbon nanotube layer are arranged side by side in thesame plane.
 12. The system as claimed in claim 1, wherein the measuringdevice is a voltage measuring device or a thermocouple device configuredto measure voltage differences or temperature differences.